The present invention relates to a method for producing a plurality of apparently independent target projection display channels from a single image generation channel and one projector.
The imagery produced by the visual display system of a flight training simulator is that imagery visible through the simulated aircraft cockpit windows, commonly consisting of real-time, computer-generated graphics projected onto a large dome-shaped screen. The background imagery portion includes those low interest peripheral and long-distance portions of the visible scene. Target imagery includes small, high interest portions of the scene, such as hostile aircraft, missiles, air and ground targets, and the like. In a typical conventional simulator system, target imagery is usually projected as an overlay onto the background imagery via slewable target projectors, one per target.
Monochrome target imagery is usually chosen for flight simulator visual systems due to the high cost of producing dynamic, full color imagery. These cost difficulties arise from the need to maintain focus and convergence in a color image that will be rapidly slewed over a large display dome projection screen. This can be achieved, but at the expense of utilizing complicated dichroic combiners, dynamic focussing, and/or intricate pointing mechanisms. The end result has been, over the years, that monochromatic target imagery is accepted by the user community primarily because it is cost-effective.
Unfortunately, the computer image generation technology has concentrated on full color systems. This leaves the system designer with the situation of being forced to satisfy a monochrome image requirement with a color system. This wastes much of the capability of the image generator, as it must work solely in grey shades or with a single primary color. The present invention allows an even more cost-effective alternative to be considered.
A conventional, full-color CRT video projector 20 is shown in block diagram form in FIG. 1, and already contains three separate video channels, one for each of the three primary colors, red, green, and blue. The system 20 comprises a conventional image generator 22, which outputs red, green, blue and synchronization (RGBS) signals 24 to an RGB color projector 26. The projector 26 includes a red CRT 28, a blue CRT 30, and a green CRT 32. The respective images from the CRTs 28, 30 and 32 combine to form a full color image in the conventional system. A pointing apparatus 34 is typically employed in a target projection system to provide positional control of the image.
The image content of the three primary color channels in the conventional system has always been assumed to be coherent. However, nothing in the technology imposes this restriction, and whatever is present on the RGB video signal inputs appears on the red-green-blue (RGB) projected display outputs of the system 20 of FIG. 1.